This invention relates to a bypass augmentation burner arrangement for a gas turbine engine and, more particularly, to a bypass augmentation burner arrangement for a gas turbine engine of the bypass type whereby spaced apart struts are provided in downstream relation to the bypass burner.
In a bypass gas turbine engine, a portion of the air entering the engine is bypassed around the compressor, the combustion stage and the turbine of the gas turbine engine. The bypassed air may be ram induction air, in which case there would be no additional thrust added to the thrust produced within the combustion stage portion of the engine. The bypass gas turbine engine may alternatively include a fan section wherein a portion of the airflow through the fan is directed to the bypass air passage. Such engines are well known to the art and commonly referred to as turbofan engines. The invention shall hereinafter be described in relation to a bypass gas turbine engine of the turbofan type, although it is understood that the broad scope of the invention is applicable to all bypass gas turbine engines.
Recently, it has been suggested that bypass augmentation burners be included in the bypass air passages of turbofan engines in order to provide additional thrust to the thrust already produced within the central combustion stage of the engine. Heretofore in gas turbine engines of the bypass type, it has been difficult, if not impossible, to station supporting struts in the bypass duct at a location downstream of the burner due to the high heat of the exhaust stream exiting from the burner. This high heat often damages the supporting struts and considerably shortens their useful lifetime. Locating the supporting struts upstream of the augmentation burner, although eliminating the danger of overheating or burning the struts incurs the disadvantage of increasing the overhanging moment between the bypass duct and core engine. This in turn reduces the overall structural integrity of the engine and may be the cause of increased vibrations encountered within the core engine.
Therefore, it is a primary object of this invention to provide a bypass burner and supporting strut arrangement for a bypass gas turbine engine whereby the supporting struts in the bypass duct may be located downstream of the bypass burner in a manner which does not permit substantial impingement of the hot gases of combustion exiting from the bypass burner on to the supporting struts.